Final answer:
Photosynthesis occurs in the chloroplasts of plant cells, within the mesophyll layer of the leaf, and in some bacteria within structures similar to thylakoids.
Step-by-step explanation:
Photosynthesis primarily occurs in the chloroplasts of plant cells and in some types of bacteria that possess a similar structure to chloroplasts. In plants, the cells that contain chloroplasts are predominantly found in the mesophyll layer of the leaf. Chloroplasts are double-membrane organelles with an internal thylakoid membrane system where chlorophyll, the green pigment essential for the photosynthesis process, is located. The light-dependent reactions of photosynthesis happen within these thylakoid membranes.
In addition to plants, some bacteria can perform photosynthesis. Cyanobacteria, for instance, contain chlorophyll and utilize similar photosynthetic mechanisms to plants for glucose production. However, in cyanobacteria, photosynthesis takes place in specialized structures called thylakoids, which are not enclosed by an additional membrane, unlike the chloroplasts in plant cells.